Transcript The Lymphatic System

The Lymphatic System
3/5/14
What is it?
• Lymphatic System = A vast collection of cells
and biochemicals that travel in lymphatic
vessels, and the organs and glands that
produce them.
• Pathogens = disease-causing agents.
Lymphatic Pathways
• Begin as lymphatic capillaries that merge to form
larger lymphatic vessels.
• Lymphatic vessels then lead to larger vessels that
unite with the veins in the thorax.
• Lymphatic capillaries – microscopic, closed-ended
tubes that extend from interstitial (“between
tissues”) spaces forming complex networks.
– They resemble the blood vessels, except they don’t
carry blood.
Lymphatic Vessels
• Lymph – fluid inside a lymphatic capillary.
• Lymphatic vessels – tube-like tunnels that
resemble blood vessels except with thinner
walls.
– Three layers
1. Endothelial layer(inner lining)
2. Smooth muscle (middle layer)
3. Connective tissue (outer layer)
Lymph Nodes
• Lymph node = specialized organs that lymph
vessels lead to.
• After leaving the lymph nodes, vessels merge
into lymph trunks.
• Lymph trunks:
– Drain lymph from the lymphatic vessels
– Named for the regions they serve
• Example: intestinal trunk drains lymph from the
abdominal area.
Ducts
• Lymphatic trunks then join 1 of 2 collecting
ducts:
1. Thoracic duct
2. Right lymphatic duct
**see figure 16.4 on pg. 619
Thoracic Duct
• = the larger and longer of the 2 collecting
ducts
• Originates in the abdomen
• Drains lymph from intestinal, lumbar, and
intercostal (rib area) trunks.
Right Lymphatic Duct
• Originates in the right thorax
• Lymph from the right side of the head and
neck, the right upper limb, and the right
thorax enters this duct.
Structure of a Lymph Node
• Lymph nodes vary in size and shape, but are
usually less than 2.5 cm (1 inch) long and are
somewhat bean-shaped.
• Hilum – indented region of the node.
• Lymph nodules – masses of lymphocytes and
macrophages in the cortex that are the
functional units of the lymph nodes.
Locations of Lymph Nodes
1.
2.
3.
4.
5.
6.
7.
Cervical Region
Axillary Region
Supratrochlear Region
Inguinal Region
Pelvic Cavity
Abdominal Cavity
Thoracic Cavity
Functions of Lymph Nodes
2 Primary Functions
1. Filtering potentially harmful particles from lymph
before returning it to the bloodstream
2. Monitoring body fluids provided by lymphocytes
and macrophages.
**Lymphocytes attack viruses, bacteria, and other
parasitic cells within the lymph nodes.
Thymus
• Thymus – soft, bilobed (2 lobes) structure
enclosed in a connective tissue capsule.
– Located anterior to the aortic arch, posterior to
the superior part of the body of the sternum.
– It varies in size, and is proportionally larger during
infancy and early childhood.
Spleen
Spleen – largest lymphatic organ and is located
in the upper left portion of the abdominal
cavity, inferior to the diaphragm, posterior and
lateral to the stomach.
– Spaces in the in the chambers of the spleen are
filled with blood.
Unit Assignment
• Do pg. 648, “Chapter Assessment”: 3-5, 7, 910, 12-14,18,28,31,39,47, and critical thinking
#4. Due Friday, March 21st by midnight.